Attic Insulation Blown In — Air Sealed First, Then Filled
Ice dams, a furnace that never shuts off, a bedroom that is cold at the ceiling: the attic is the first place to look and the best payback in the house when the air sealing is done before the fluff.
JMB Builders blows in attic insulation across the Twin Cities metro, and air-seals the attic floor first because loose insulation does nothing against a draft. Top plates, wire and pipe holes, the chimney chase, can lights and the hatch get sealed, baffles go in at every soffit bay, then cellulose or fiberglass is blown to the code range for a Minnesota attic. Priced per project, quoted from your attic photos and a rough square footage within one business day.
- Air sealing before insulation, every time
- Cellulose or fiberglass, blown to the code range
- Quote from attic photos in 1 business day
- Licensed MN contractor BC809005
Most Twin Cities attics have some insulation and not enough, and what is there is doing half the job because warm air is going straight through it. Every hole in the ceiling, from the top of every interior wall to the plumbing stack, the bath fan, the chimney chase and the attic hatch, is a chimney that pulls heated air out of the house and dumps it into the attic. That air melts the snow and makes the ice dam. Blowing more insulation over the holes hides them; it does not close them.
So the job is in two parts. Air sealing first: we pull back the existing insulation where it needs to be, foam or caulk every top plate and penetration, box or cover the recessed lights with covers made for it, seal the chase around the chimney with sheet metal and high-temperature sealant, and weatherstrip and insulate the hatch or the pull-down stairs. Then baffles at every rafter bay so the blown insulation cannot slide down and block the soffit vents. Then the blower: cellulose or fiberglass to the depth marked on the rulers we staple to the trusses, so you can see the level from the hatch.
Old insulation usually stays and gets topped. The exceptions are wet insulation, insulation with rodent damage, and vermiculite, which has to be tested and handled by an abatement contractor before anyone works up there. We look at that in your photos before we quote.
What you supply
- Photos from the attic hatch: the insulation depth, a top plate if visible, any can lights and the soffit edge
- The rough footprint of the house so we can estimate the attic area
- Clear access to the hatch; we cover the floor and stairs below it
- Whether there is vermiculite (gray-brown pebbles), knob-and-tube wiring or a bath fan venting into the attic
What JMB supplies
- Air sealing of top plates, penetrations, the chimney chase, can lights and the hatch with foam, caulk and covers
- Baffles at every soffit bay and a dam around the hatch so insulation stays where it belongs
- Blown cellulose or fiberglass to the code range for Minnesota, with depth rulers left in place
- Insulated, weatherstripped hatch cover or pull-down stair cover
- Bath fan ducts rerouted to a roof or gable cap if they end in the attic
- Floor and stair protection, cleanup of the hallway under the hatch
- Before and after photos from the attic in your job folder
How it is priced: per project
Quoted in writing from your photos within one business day. What moves the number:
- Attic square footage and the depth needed to reach the code range from what is there now
- How much air sealing the ceiling needs; a house full of recessed lights and a chimney is more than a plain ceiling
- Cellulose vs. fiberglass
- Baffles: how many rafter bays and whether the soffit vents are open or blocked
- Whether the hatch or pull-down stair needs a new insulated cover
- Bath fan ducts that need to be rerouted out of the attic
- Access: a tight hatch or a story-and-a-half with kneewall attics takes longer
- Removal of wet or rodent-damaged insulation before the new goes in
One photo down the hatch showing the insulation depth against a truss, and the house footprint, gets you the quote. Tell us about vermiculite or knob-and-tube if you see either.
How long it takes
Air sealing and blow-in on a typical attic: one day. Larger attics or ones needing a lot of sealing and new baffles: two days.
How your project works
- 1
Send photos, get a written quote
Send three photos of the space and a sentence about what you want. You get a clear, itemized quote within one business day. We only come out to measure first when the job needs a tape measure — no pressure, no games.
- 2
Pick materials, or bring your own
We help you choose profiles and materials that fit the house and the budget, or match your existing millwork exactly — or you buy the door or trim yourself and we install it. Everything is confirmed before the crew is scheduled.
- 3
Clean, precise installation
The crew shows up on time, protects floors and furniture, and installs with tight joints and consistent reveals. Photos of the finished work go in your job folder.
- 4
Walkthrough and invoice
We walk the finished work with you. If anything is not right, we fix it before we call the job done. Then one invoice, paid by check or direct deposit — no card fees, no payment links.
Situations and options
Cellulose blow-in
Recycled paper treated with borate, blown dense. It fills around framing and wires better than fiberglass, slows air movement more, and is the usual pick for topping an existing attic. Slightly heavier, so the ceiling drywall has to be sound.
Fiberglass blow-in
Loose fiberglass blown to depth. Lighter, does not settle as much and is the choice where the ceiling is marginal or the attic is also used for storage on a raised platform. It relies more on the air sealing under it, which we do either way.
Air sealing only
When the insulation depth is already fine but the ice dams or drafts say the air is getting through anyway. We pull it back at the walls, seal, and put it back. A half-day job on many houses and often the part that makes the difference.
Kneewall and story-and-a-half attics
Cape Cod and story-and-a-half houses have short side attics behind kneewalls and a flat attic above. Each part needs its own approach: sealing and insulating the kneewall and the floor behind it, baffles up the slope, and blow-in on top.
Attic Insulation Blown In — Air Sealed First, Then Filled: questions, answered
How much attic insulation do I need in Minnesota?
The Minnesota code sets a range for attic insulation and most older houses are well under it. The quick test is to look down the hatch: if you can see the tops of the ceiling joists or trusses, you are short. We measure the depth of what is there, figure what it takes to reach the code range with the material chosen, and staple depth rulers to the trusses so you can check it yourself after.
Cellulose or fiberglass for a blown-in attic?
Both work when the air sealing under them is done. Cellulose packs tighter, blocks air movement better and fills odd spaces around wires and framing; it is our usual choice for topping an existing attic. Fiberglass is lighter and settles less, which matters on a ceiling that is already sagging or an attic used for storage. We quote either, and the difference in price is small next to the labor.
Why air seal the attic before adding insulation?
Because insulation slows heat, not air. Warm air leaving through gaps at the top plates, can lights and the hatch carries heat and moisture straight into the attic no matter how deep the insulation is. That air is what melts the roof snow into ice dams. Sealing the gaps first is a few hours of work with foam and caulk and it is the part of the job with the biggest effect.
Do I need to remove the old attic insulation?
Usually not. Dry, clean existing insulation stays and the new is blown over it after we pull it back to seal the top plates. Remove it when it is wet, when animals have been in it, or when it is vermiculite, which can contain asbestos and must be tested and removed by an abatement contractor before anyone disturbs it. We check for all three in your photos.
Can you insulate around recessed lights in the attic?
Only if the fixtures are rated for insulation contact, or they get a cover. Older can lights are not rated and they need clearance, which leaves a hole in the insulation at each one. We put a fire-rated cover over each can, seal the cover to the drywall, and blow over it. Replacing old cans with sealed LED retrofits is an electrician's job we can coordinate.
Will adding attic insulation stop my ice dams?
Insulation plus air sealing plus ventilation will. Insulation alone slows the heat; air sealing stops the warm air; baffles and open soffit vents let whatever heat gets through leave before it warms the roof. Skipping any of the three leaves the dam. If the eave is already damaged, see the ice dam repair page; that gets fixed first and this gets done the same week.
Get a written quote for this job
Three photos and a sentence is enough. You hear back within one business day. Or text the photos to 763-204-2099.
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Read morePage reviewed September 24, 2026 · JMB Builders LLC, MN license BC809005 · All insulation pages
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Based in Zimmerman, scheduling across the Twin Cities metro. Closest first: